Apparatus for video printing

Abstract: A video signal printing apparatus comprises a cassette (1) comprising a supply reel (13), a take-up reel (14), and a ribbon (10) wrapped around said reels; a main chassis (401) for receiving said cassette; a capstan (410) and a pinch roller (411) for feeding a paper (202) to a paper printing position; a motor means for rotating said capstan (410) and said pinch roller (411); a platen for receiving the paper in said paper printing position, said platen being disposed in a position downstream of said capstan (410) and pinch roller (411) in a feeding direction; a head means (323) for heating and pressing said ribbon (10) onto the paper (202) in said printing position, said head means (323) being movable between a head printing position in which said ribbon is pressed onto said paper and a head waiting position in which said head releases said ribbon from said paper; and a control means (308) for selectively moving said head means (323) between said head printing position and said head waiting position, and for causing a slack of the ribbon to wind up onto said supply reel (13) upon said head means moving to said head waiting position.

Description: FIELD OF THE INVENTION The present invention relates generally to a printer for saving a recording picture, such as a video picture or the like, as a hard copy, and particularly to a sublimation type thermal transfer system video printer for producing a hard copy of a video picture. DESCRIPTION OF THE RELATED ART Conventional video printers include a gear mechanism for searching a head of an ink ribbon of a ribbon cassette housed in the printer and taking up the ink ribbon by a take-up reel during a printing operation using a DC motor as a drive source. These printers typically include a gear mechanism for feeding a printing paper housed in a tray, and a cam mechanism for pressing the ink ribbon on the printing paper and moving a printing head, which subjects the printing paper to a printing processing. A DC motor is provided for moving the printing head and for use as a drive source to rotate a capstan for carrying the printing paper to a printing position and a paper delivering position successively. A complex cam mechanism and a link mechanism are required to drive the paper feeding mechanism, the cam mechanism and the printing head with a single drive motor. Other printer devices include a stepping motor as a second drive source for driving one or more of the printer mechanisms. These conventional printers suffer from a linkage and drive mechanism which is complex and space consuming and fails to provide effective operation in the event of paper jams or other interruptions during normal printing operations. Thus, one object of the present invention is to provide a printer construction whereby miniaturisation of the printer can be realised and printer operations can be enhanced under adverse conditions. Another problem with conventional video printers is that they waste printer ribbon between successive printing operations. Conventional printers typically include a mechanism for holding a printing paper and an ink ribbon between a printing head and a platen and use a stepping motor as a drive source and a cam mechanism for pressing and heating the ink ribbon on the printing paper for printing processing. When the ink ribbon is released from the printing paper, it has a slack between the supply reel and the take-up reel of the ribbon cassette. This slack is typically removed by winding the ribbon in the direction of winding during the printing operation, thereby increasing the amount of ribbon required for printing. In addition, identification systems on ribbon cassettes often require rotation of the take-up and/or supply reels resulting in further waste of the ink ribbon. Accordingly, it is a further object of the present invention to eliminate wasteful usage of ink ribbon in printer devices. Yet another problem with conventional video printers is that the printer head moving mechanism is typically interconnected with the paper moving mechanism or the ribbon identification mechanism such that the printing head cannot be moved independent of those mechanisms. This results in unnecessary movement of the printing head during paper feeding and ribbon identification, and restricts the use of the printing head for guiding the printing paper into a printing position. Thus, a further object of the present invention is to provide a driving mechanism for a printer which allows the printing head to be freely moved while maintaining a compact printer arrangement. EP-A-413 358 discloses a known printing apparatus comprising all the features of the apparatus specified in the preamble of claim 1. SUMMARY OF THE INVENTION In order to achieve the above-mentioned objects, in a printer for producing a hard copy of a recording picture, the printer according to the present invention is specified in claim 1. This printer comprises a normally and reversely rotatable first drive motor for searching a head of an ink ribbon of a ribbon cassette housed in the printer and for taking up the ink ribbon by a take-up reel during a printing operation, a normally and reversely rotatable second drive motor for feeding a printing paper housed in a tray through a carrying roller by a capstan and a pinch roller to a printing position and a paper delivering position, and a normally and reversely rotatable third drive motor for identifying the ink ribbon by a ribbon code ring and for moving a printing head, which subjects the printing paper to a printing processing, by pressing the ink ribbon thereon with a platen. According to the printer of the present invention constructed as described above, first, in order to detect a header mark of the ink ribbon in the ribbon cassette, the take-up reel is rotated by the first drive motor to take up the ink ribbon by a predetermined amount, and then the head of the ink ribbon is searched. Next, the printing paper housed in the tray is carried by the capstan through drive of the second drive motor and carried to the printing position with a length of the printing paper discriminated. Then, when it is determined that the printing paper has a length of a regular paper, under such a state that the printing head moved through a cam mechanism rotated by drive of the third drive motor is pressed on the printing paper through the ink ribbon, the printing paper and the ink ribbon are carried and subjected to the printing processing. As explained above, in the printer for producing the hard copy of the recording picture, the printer according to the present invention is formed of the normally and reversely rotatable first drive motor for taking up the ink ribbon of the ribbon cassette housed in the printer by the take-up reel, the normally and reversely rotatable second drive motor for feeding the printing paper housed in the tray through the carrying roller by the capstan roller and the pinch roller to the printing position and the paper delivering position, and the normally and reversely rotatable third drive motor for moving the printing head which subjects the printing paper to the printing processing by pressing the ink ribbon thereon with the platen roller. Therefore, even in case of the jam of the printing paper, interruption during the printing operation or the like, the printing paper can be carried and the ink ribbon can be taken up while the head is being moved at the most proper timing, so that when the power source is supplied again, operation can be automatically restored. Also, the miniaturisation of the printer can be realised. The head can also be freely moved, whereby the printing paper can be pushed down and the passage of the paper can also be provided at the printing unit. Therefore, the printer can be further miniaturised. Also, when the printing paper and the ink ribbon are not matched with each other, the printing paper is automatically delivered and the ink ribbon is rewound, whereby the wasteful use of the ink ribbon can be prevented. BRIEF DISCLOSURE OF THE DRAWINGS Figure 1 is a perspective view of an appearance of a printer according to the present embodiment. Figure 2 is a partially cross-sectional, side view of the printer according to the present embodiment. Figure 3 is a cross-sectional view in which the printer according to the present embodiment is cut at a portion of a cam 308. Figure 4 is a cross-sectional view in which the printer according to the present embodiment is cut at a portion of a gear 305. Figure 5 is a side view of a transmission mechanism system to a T reel base, an S reel base and a change arm. Figure 6 is a perspective view of a ribbon cassette. Figure 7 is a partially cross-sectional, plan view of the ribbon cassette. Figure 8 is a perspective view of an ink ribbon. Figure 9 is a perspective view of a ribbon door and a ribbon-door holder. Figure 10 is a cross-sectional view of the ribbon door. Figure 11 is a detailed diagram of the T reel base. Figure 12 is a detailed diagram of a gear 109. Figure 13A to 13C are operational diagrams of a relation between a sensor and a paper position. Figure 14 is an exploded and perspective view of a paper feeding cam and a releasing cam and counterparts thereof. Figure 15 is a detailed diagram of a two-stage gear 132. Figure 16 is a detailed diagram of the S reel base. Figure 17A to 17D are diagrams of respective relations of respective stop positions H0 to H4 of the gear 305 and rotation positions of a cam groove 308a, a cam groove 308b and a cam groove 309a. Figure 18A to 18D are diagrams of respective relations of stop positions H2a and H2b of the gear 305 and the rotation positions of the cam groove 308a, the cam groove 308b and the cam groove 309a. Figure 19 is a detailed diagram of the cam groove 308a. Figure 20 is a detailed diagram of the cam groove 308b. Figure 21 is a detailed diagram of the cam groove 309a. Figure 22 is an exploded perspective view of a mechanism unit of a head arm portion. Figure 23A to 23D are diagrams of positional relation of the cam groove 308a and a head 323 upon respective operations. Figure 24A to 24B are diagrams of respective operations of the change arm. Figure 25A and 25B are diagrams of relation of operation of the cam groove 309a and a pendulum gear 330 and a locking lever 332. Figure 26 is a diagram of operation of a head position H0 and a paper position P0 of the printer. Figure 27 is a diagram of operation of a head position H2 and a paper position P0 of the printer. Figure 28 is a diagram of operation of the head position H2 and a paper position P1 of the printer. Figure 29 is a diagram of operation of a head position H3 and a paper position P2 of the printer. Figure 30 is a diagram of operation of a head position H4 and the paper position P2 of the printer. Figure 31 is a diagram of operation of the head position H2 and the paper position P2 of the printer. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS An embodiment of the printer according to the present invention will hereinafter be explained with reference to the accompanying drawings by referring to a sublimation type thermal transfer system video printer as an example. Figure 1 is a perspective view of an appearance of a video printer of the present embodiment. Reference letter A represents the whole of the video printer (hereinafter referred to simply as printer). A case body of the printer A is formed of an upper case 701 and a lower case 702 which are made of plastic. On a rear side of a side portion of the printer A, an ink ribbon door 420 for housing an ink ribbon cassette (hereinafter referred to as ribbon cassette), which will be described later, in the printer A is provided in such a manner that it can be opened and closed. Also, on a front surface side of the printer A, there are provided a paper feeding tray 200, a paper delivering opening 703 for a printing paper, an input terminal 704 for a video signal, a power-source switch 705 and various kinds of switches 706 for determining a picture to be printed and designating the number of printing papers to be printed or the like. The paper feeding tray 200 can be drawn and inserted by opening a paper door 702a of the lower case 702 and a paper delivering cover 701a of the upper case 701. Figures 2, 3, 4 and 5 are different cross-sectional side views of cutting portions of the printer A. A chassis 401 which is bent so as to have a shape of a letter U is provided therein. A cover plate 404 is fitted to an upper opening portion of the chassis 401, and a bracket 100 and a rear-surface bracket 301 are fitted to side surfaces thereof. In the figures, a ribbon cassette I is housed through a side-surface opening portion 401a of the chassis 401, and the above-mentioned paper feeding tray 200 is loaded through a front-surface opening portion 401b in such a manner that it can be freely attached and detached. Into a rectangular aperture through a bottom surface of the paper feeding tray 200, a paper feeding plate 201 and clicks 201a and 203a of a pair of left and right holding clicks 203 are inserted. The paper feeding plate 201 and a pair of the holding clicks 203 are rotated by a paper feeding arm 204 (see Figure 4) rotated by a cam, which will be described later. The respective clicks 201a and 203a are used as fulcrums to press an end portion of a printing paper 202 in the paper feeding tray 200 on a paper feeding roller 213. Also, the paper feeding tray 200 is guided by a rail (not shown) and loaded at a predetermined position in the printer. While a locking click 209 is rotated by operation of the cam, which will be described later, during a paper feeding operation, the locking click 209 is engaged with an aperture 200a of the paper feeding tray 200 to thereby prevent the paper feeding tray 200 from being drawn. If roughly classified, the printer A as described above is formed of an ink ribbon mechanism using as a drive source a DC motor for searching a head of an ink ribbon in the ribbon cassette 1 and for taking up and rewinding the ink ribbon during a printing operation, a printing-paper feeding and delivering mechanism using as a drive source a stepping motor for feeding the printing paper in the tray 200 to a printing position and drawing the printing paper, which has been subjected to a printing processing, through the paper delivering opening 703 and a head mechanism using as a drive source a DC motor for performing the printing processing by a line type thermal head (hereinafter referred to simply as head). Hereinafter, the above-mentioned ink ribbon mechanism, printing-paper feeding and delivering mechanism and head mechanism will successively be explained. The ribbon cassette 1 for use in the present invention will be explained in detail with reference to Figures 6 to 8. A cassette body 2 of the ribbon cassette 1 is formed so as to have a shape of such a case that a lower case 3 made of synthetic resin and an upper case 4 made of synthetic resin have a rectangular opening at a center portion thereof and an ink ribbon 10a to be used of an ink ribbon 10 is exposed through an opening portion 4a. One pair of bearing portions 5a and 5b formed by the lower case 3 and the upper case 4 rotatably support one end portion 15 and a shaft end 17 of a supply spool 13 around which an unused ribbon 10b is wound, and the other pair of bearing portions 6a and 6b rotatably support an end portion 16 and a shaft end 18 of a take-up spool 14 for taking up a used ribbon 10c. Also, the above-mentioned supply spool 13 and the take-up spool 14 are biased by compression coil springs 7 and 8 toward sides of one bearing portions 5a and 6a, respectively. A code ring 21 is rotatably fitted to the supply spool 13 so as to be coaxial relative to the supply spool 13. The code ring 21 has on an outer periphery thereof a gear portion 22 and an information code 23 indicating information such as kinds, sensitivity, number or the like of the ink ribbon 10. Even in a stop state of the supply spool 13, the code ring 21 can be rotated by driving the gear portion 22 from the outside of the ribbon cassette 1. On the other hand, when the code ring 21 does not receive any force from the outside of the ribbon cassette 1, it is rotated by a friction force between the supply spool 13 and the code ring 21 in a similar way to rotation of the supply spool 13. In the ink ribbon 10, a header mark 11 indicating a writing position of the ribbon upon a printing is printed over an entire width of the ink ribbon 10, and a patch mark 12 indicating a writing position of each colour ribbon 10d in case of a multi colour ribbon is printed over a half width of the ink ribbon 10. Also, the cassette body 2 is provided with an aperture 19 and an aperture 20, which are engaged with cassette pins 402 and 403 to thereby position the cassette body when the cassette body is loaded on the printer. Explanation about the ribbon door 420: A portion through which the ribbon cassette 1 is loaded on and unloaded from the printer will be explained with reference to Figures 9 and 10. An entrance guide 426 is provided at the printer-front-surface opening portion 401a. The ribbon door 420 is rotatably fitted to the entrance guide 426 about a shaft 425. A locking click 421 is provided at the ribbon door 420. The click 421 is engaged with an aperture 422a of a ribbon-door holder 422 to thereby close the ribbon door 420. The click is biased by a spring 430 so as not to come out of the aperture. By pushing an external portion 421a of the locking click 421 down, the engagement of the locking click 421 and the aperture 422a is released to open the ribbon door 420. The ribbon cassette 1 is guided by the guide 426, inserted into and loaded on a cassette housing portion 405. If the ribbon door 420 is closed under this state, then the ribbon door 420 is locked by the locking click 421 and the loaded ribbon cassette 1 is biased in a direction to the inside of the printer by a ribbon holder 423 biased by a spring 424 projecting toward a rear-surface side of the ribbon door 420. Explanation about a locking lever of the ribbon door 420; During the printing, in order to prohibit ejection of the ribbon cassette 1, a locking lever 332 fitted to the ribbon door 420 is positioned on the side below the locking click 421 to restrict a downward movement of the locking click 421 by the action of a cam described later on. Therefore, during the printing, the external portion 421a of the locking click cannot be pushed down and the locking click 421 is prevented from being released, so that the ribbon door 420 cannot be opened, whereby the ribbon cassette 1 cannot be ejected. Next, there will be explained an operation of the ink ribbon mechanism by the DC motor as a drive source. First, there will be explained a portion which is driven by rotation of a motor 101. The motor 101 can be rotated normally and reversely. A transmission course of rotation thereof is switched between a normal rotation thereof and a reverse rotation thereof which are based on operation of a pendulum gear 107. The rotation is transmitted to the take-up spool 14 of the ribbon cassette 1 through a take-up reel base 111 (hereinafter referred to as T reel base 111) by one direction of rotation thereof and to a cam 416 of a printing-paper carrying mechanism by the other direction of rotation thereof. Explanation about transmission of rotation to the take-up spool 14: The rotation of the motor 101 is transmitted to a worm 104 through a worm base 103 forced onto a shaft of the motor 101 and reduced by a two-stage gear 105 and a two-stage gear 106. A friction force is generated by a spring or the like (not shown) between the pendulum gear 107 and a pendulum-gear arm 108. Therefore, if the two-stage gear 106 is rotated in the clockwise direction in the figure, then the pendulum-gear arm 108 is also rotated in the same direction to engage the pendulum gear 107 with a gear 109, whereby the rotation is transmitted to a gear 110. The gear 110 is a part having torque limiting function and constructing the T reel base 111. A cross section of the T reel base 111 is shown in Figure 11. Felts 110a and 110b are respectively bonded to front and rear surfaces of the gear 110 and can be rotated together with a pressure plate 112 using a hollow shaft 111c as a shaft. An engaging portion 111b which is a torque transmission unit between a gear portion 111a and the take-up spool 14 of the ribbon cassette 1 is forced into the shaft 111c to thereby rotate the gear portion 111a, the engaging portion 111b and the shaft 111c integrally. The pressure plate 112 is engaged with the engaging portion 111b at their convex-concave portions to thereby rotate the former in the same direction as the engaging portion 111b. A compression coil spring 113 is disposed between the engaging portion 111b and the pressure plate 112 and puts pressure to the felt 110a and the pressure plate 112 and the felt 110b and the gear portion 111a to generate a friction force. When the gear 110 is rotated, a torque generated from the friction force is transmitted to the engaging portion 111b. However, even if a torque exceeding the torque generated by the friction force is intended to be transmitted to the engaging portion 111b, slips are generated between the felt 110a and the felt 110b and respective counterparts thereof, so that the torque exceeding the torque generated by the friction force cannot be transmitted. Also, an outside diameter of the engaging portion 111b is engaged with a bore of an engaging portion 14a of the take-up spool 14 and positions a rotation shaft of the take-up spool 14. A convex portion 111d of the engaging portion 111b is engaged with the engaging portion 14a to transmit rotation to the take-up spool 14. Explanation about a reverse-rotation preventing click of the T reel base 111: Also, a click 114 is rotatably fitted to the gear 109 on the same plane as the gear portion 111a. A felt 114a is bonded to the click 114 as shown in Figure 12. A compression coil spring 115 biases the click to thereby generate a friction force between the felt 114a and the gear 109, so that the click 114 is also rotated in the same direction as the rotation direction of the gear 109. If the two-stage gear 106 is rotated in the clockwise direction in the figure, then the gear 109 is rotated in the clockwise direction in the figure through the pendulum gear 107 and the click 114 is also rotated in the same direction. The click 114 is restricted in rotation amount by an aperture 100a of the bracket 100 and hence is prevented from being rotated unnecessarily. Function of the click 114 will be described later. Explanation about transmission of rotation to a paper position: If the two-stage gear 106 is rotated in the counterclockwise direction in the figure, then the pendulum-gear arm 108 is rotated in the same direction as the two-stage gear 106 to engage the pendulum gear 107 with a gear 116. Explanation about the reverse-rotation preventing click: At this time, if the take-up spool 14 of the ribbon cassette 1 is reversely rotated by vibration, static electricity or the like of the printer and hence slack of the ribbon is about to be produced, then the T reel base 111 is also reversely rotated and hence the gear 109 is about to be rotated in the counterclockwise direction in the figure. However, since the click 114 is similarly rotated in the same direction as the gear 109, the click 114 is engaged with the gear portion 111a of the T reel base 111 and prevents the T reel base 111 from being rotated to thereby prevent the slack of the ribbon. (When the pendulum gear 107 is engaged with the gear 109, the reversal rotation of the T reel base 111 is transmitted to respective gears to intend the worm 104 to be rotated. However, since the worm 104 is a single worm, the worm 104 is not rotated by rotation of the two-stage gear 105. Therefore, the T reel base 111 cannot be reversely rotated, and the slack of the ribbon is not produced.) Continued explanation about movement of the paper position: The rotation of the gear 116 is transmitted to a gear 118 through the gear 117. A reflection seal 119 is bonded to the gear 118, and a rotation position thereof is checked by two optical sensors 120a and 120b. Relation between the gear 118 and the sensors 120a and 120b is shown in Figure 13. The reflection seal 119 is formed of an aluminum plate having a high optical reflectance at its surface or the like, where two black portions 119a and 119b having low optical reflectance are printed. The sensors 120a and 120b detect the black portions and an aluminum surface as shade and light, respectively. The gear 118 can be rotated by function of the pendulum gear 107 only in the counterclockwise direction in the figure, and rotation thereof is stopped at a position where the sensors 120a and 120b detect the shade and the light, respectively. This position is referred to as a paper position 0 (hereinafter referred to as P0) (Figure 13A). Next, the gear 118 is rotated by 120°, and the rotation thereof is stopped at a position where the sensors 120a and 120b detect the light and the shade, respectively. This position is referred to as a paper position 1 (hereinafter referred to as P1) (Figure 13B). Subsequently, the gear 118 is rotated by 120°, and the rotation thereof is stopped at a position where both of the sensors 120a and 120b detect the shade. This position is referred to as a paper position 2 (hereinafter referred to as P2) (Figure 13C). If the gear 118 is rotated by a further 120°, then the sensors detect the P0 position again. Therefore, the gear 118 circulates through the respective positions of P0, P1, P2, P0, ..., and hence can be moved to and stopped at an optional position. Movement of the cam and its counterpart at the paper position: As shown in Figure 14, the gear 118 is connectably rotated by a shaft 418 which is supported by the chassis 401 for a paper feeding cam 416 and a pair of releasing cams 417 to be rotatably supported. As shown in Figure 14, a pressing plate 205 and the locking click 209 are rotated by a cam plane 416a of the paper feeding cam 416 and a cam plane 416b thereof, respectively. A releasing lever 222 and a pinch-roller arm 413 are rotated by a cam plane 417a of the releasing cam 417 and a cam plane 417b thereof, respectively. Explanation about function of the paper feeding cam 416: As shown in Figure 14, the pressing plate 205 is rotatably fitted to a shaft 208 fitted to the paper feeding arm 204 and the locking click 209. The pressing plate 205 and the locking click 209 are respectively biased by a spring 207 and a spring 210 in the direction of the paper feeding cam 416. The paper feeding arm 204 is pressed by a torsion coil spring 206 on the pressing plate 205 and also restricts a relative position. When the pressing plate 205 is rotated by the cam plane 416a of the paper feeding cam 416, the paper feeding arm 204 is similarly rotated to bring the paper feeding plate 201 upward, and the printing paper 202 in the paper feeding tray 200 is brought in contact with the paper feeding roller 213. Further, when the pressing plate 205 is rotated, the paper feeding arm 204 is in contact with the paper feeding roller 213 and restricted in movement by the paper feeding plate 201 whose rotation has become impossible. A relative difference in rotation is caused between the pressing plate 205 and the paper feeding arm 204 to generate flexure in the spring 206. The paper feeding arm 204 puts a pressure on the paper feeding plate 201 by a spring force of the spring 206 to press the printing paper 202 on the paper feeding roller 213. Also, the locking click 209 is rotated by the cam plane 416b of the paper feeding cam 416 and then engaged with the aperture 200a of the paper feeding tray 200 to thereby prevent the paper feeding tray 200 from being removed. Explanation about movement of the releasing cam 417: The pinch-roller arm 413 rotatably supported by the chassis 401 supports a pinch roller 411 rotatably so that the pinch roller 411 is pressed on a capstan 410 by a spring 414. The pinch-roller arm 413 is rotated by operation of the releasing cam 417 to release the pressing of the pinch roller 411 on the capstan 410. The releasing lever 222 is rotatably fitted to a shaft 218 fitted to the chassis 401 and biased by a spring 223 in the direction of the releasing cam 417. The releasing lever 222 is rotated by the releasing cam 417 and rotates a rotating plate 215, which supports a separating roller 214 rotatably, through a spring 217 to thereby press the separating roller 214 on a paper feeding roller 212 and open a shutter 221 which is rotatably fitted to a shaft of the paper feeding roller 212 and closed by a spring 220. Also, the spring 220 biases a holding lever 219 rotatably fitted to the paper feeding roller 213. A standby position of the holding lever 219 is determined by restriction of a guide 211. There will be explained in detail later a driving method or the like of the paper feeding roller 212, the paper feeding roller 213 and the separating roller 214. Next, there will be explained operation of a stepping motor for driving a printing-paper feeding and delivering mechanism. A controlling circuit enables a stepping motor 102 to be rotated normally and reversely by angles of an optional multiple of a step angle peculiar to the motor. The stepping motor 102 carries the printing paper 202 in co-operation with the above-mentioned paper feeding cam 416 and releasing cam 417 and rotates a supply reel base 146 (hereinafter referred to as S reel base 146) in co-operation with a link 149, which will be described later, or the like. Explanation about a paper carrying system: Rotation of a pinion 121 forced onto a rotation shaft of the stepping motor 102 is reduced by a two-stage gear 122 and then transmitted to a gear pulley 123. A pendulum gear 124 is connected to the gear pulley 123 through a pendulum arm 125. operation of the pendulum gear 124 will be described later. Rotation of the gear pulley 123 is transmitted by a belt 126 to a gear pulley 127. The gear pulley 127 rotates the capstan 410 carrying the printing paper. The capstan 410 is a roller which is rotatably supported by the chassis 401 through a bearing (not shown) and whose surface is subjected to such a working that a friction coefficient thereof relative to the printing paper becomes large. The rotation of the gear pulley 127 is also transmitted to a two-stage gear 132 through a gear 129 and a gear 130. The two-stage gear 132 is a part constructing a paper feeding limiter 131 having a torque limiting mechanism shown in Figure 15 which is a cross-sectional view thereof. The two-stage gear 132 and a pressure plate 134 to which a felt 134a is bonded employ a hollow shaft 133a, which is a part of a gear 133, as a rotation shaft. A holding plate 135 is forced into the shaft 133a, and the gear 133 and the holding plate 135 are integrally rotated. The holding plate 135 and the pressure plate 134 are rotated in the same direction by engagement thereof at respective convex and concave portions. A compression coil spring 136 is disposed between the pressure plate 134 and the holding plate 135 and puts pressure to the two-stage gear 132 and the felt 134a, and the two-stage gear 132 and the felt 134a to generate a friction force. When the two-stage gear 132 is rotated, a torque produced by the friction force is transmitted to the gear 133. However, even if a torque exceeding the torque generated from the friction force is intended to be transmitted to the gear 133, slips are generated between the two-stage gear 132 and a counterpart thereof, so that the torque exceeding the torque generated by the friction force cannot be transmitted. Rotation of the two-stage gear 132 is transmitted to a gear 137, a gear 139, a two-stage gear 140 and a gear 141. Rotation of the gear 133 is transmitted to a gear 138. Rotation of the gear 137, rotation of the gear 138, rotation of the two-stage gear 140 and rotation of the gear 141 are transmitted to the paper feeding roller 212, the separating roller 214, the paper feeding roller 213 and a paper delivering roller 225, respectively. The paper feeding roller 212, the paper feeding roller 213 and the paper delivering roller 225 are rotatably supported by the guide 211 through a bearing, and the separating roller 214 is rotatably supported by the rotating plate 215 through a bearing. Explanation about the rewinding of the ink ribbon: Next, operation of the pendulum gear 124 will be explained. A friction force is generated between the pendulum gear 124 and the pendulum arm 125 by a spring or the like (not shown). Therefore, while the pendulum arm 125 is rotated in the same direction as a rotating direction of the two-stage gear 122, a shaft 125a of the pendulum arm can be moved only within an aperture 100b of the bracket 100 to thereby restrict a rotation range of the pendulum arm 125. If the two-stage gear 122 is rotated in the clockwise direction in the figure, then the pendulum arm 125 is rotated in the counterclockwise direction and restricted in rotation by the aperture 100b to race the pendulum gear 124 (i.e., enable the gear 124 to rotate without driving anything). Next, if the two-stage gear 122 is rotated in the counterclockwise direction in the figure, then the pendulum arm 125 is rotated in the clockwise direction to engage the pendulum gear 124 with a gear 145 of the S reel base 146. Explanation about the S reel base: Here, a cross section of the S reel base 146 will be explained with reference to Figure 16. The S reel base 146 has a torque limiting function. Felts 145a and 145b are respectively bonded to front and rear surfaces of the gear 145, which can be rotated together with a pressure plate 147 by using a hollow shaft 146c as a rotation shaft. An engaging portion 146b, which is a torque transmission unit between a gear portion 146a and the supply spool 13 of the ribbon cassette 1, is forced into the shaft 146c to thereby rotate the gear portion 146a, the engaging portion 146b and the shaft 146c integrally. The pressure plate 147 is engaged with the engaging portion 146b at their convex-concave portions to thereby be rotated in the same direction as the engaging portion 146b. A compression coil spring 148 is disposed between the engaging portion 146b and the pressure plate 147 and puts pressure on the felt 145a and the pressure plate 147, and the felt 145b and the gear portion 146a to generate friction forces. When the gear 145 is rotated, a torque produced from the friction force is transmitted to the engaging portion 146b. However, even if a torque exceeding the torque generated by the friction force is intended to be transmitted to the engaging portion 146b, slips are generated between the felt 145a and the felt 145b and respective counterparts thereof, so that the torque exceeding the torque generated by the friction force cannot be transmitted. An outside diameter of the engaging portion 146b is engaged with a bore of an engaging portion 13a of the supply spool 13 and positions a rotation shaft of the supply spool 13. A convex portion 146d of the engaging portion 146b is engaged with a concave portion 13b of the engaging portion 13a to transmit rotation. Continued explanation about the rewinding of the ribbon: The pendulum gear 124 transmits rotation through the above-mentioned operation thereof to the gear 145 to rotate the S reel base 146 and rotate the supply spool 13. Therefore, the ribbon 10 can be taken up (rewound) around the supply reel 13. But, a link 149 may be moved causing a head portion 149a of the link 149 to narrow a movable range of the shaft 125a of the pendulum arm to make it impossible to engage the pendulum gear 124 with the gear 145, whereby the pendulum gear 124 races (i.e., rotates without driving anything). A moving means of the link 149 will be described later. Next, operation of a DC motor for driving a head mechanism will be explained. A normally and reversely rotatable motor 300 is fitted to the bracket 301, is reduced in speed and rotates a gear 305. Explanation about transmission of rotation to the head position: A pinion 300a forced onto a shaft of the motor 300 is reduced in speed by a two-stage gear 302, a two-stage gear 303 and a two-stage gear 304 and transmits rotation thereof to the gear 305. A seal 307 is bonded to the gear 305 and checked by two optical sensors 306a and 306b. The seal 307 is formed of an aluminum plate or the like having high optical reflectance, upon which black portions 307a, 307b and 307c having low optical reflectance are printed. The sensors 306a and 306b detect the aluminum plate and printed portions as light and shade, respectively. The gear 305 is connected with a cam 308 and a cam 309 through a shaft 310. On the inner surface side of the cam 308, a cam groove 308a for rotating one head arm 312 of a pair of the head arms 312 is provided. On the outer surface side of the cam 308, a cam groove 308b for rotating a change arm 142 is provided. on the inner surface side of the cam 309, a cam groove (not shown) for rotating the other head arm 312 is provided. On the outer surface side of the cam 309, a cam groove 309a for rotating a cam lever 328 and a gear portion 309b for transmitting rotation to a two-stage gear 329 are provided (see Figure 2). The cam groove 308a and the cam groove, not shown, for rotating a pair of the head arms 312 are a pair of the cam grooves, each of which operates in the same way, so that only the cam groove 308a will be explained in the following explanation. Explanation of the head position: Five stop positions are set in the gear 305, and movement thereof to respective set positions and a setting method of the positions will be explained with reference to Figure 17A. First, in order to detect a reference position, the gear 305 is rotated in the clockwise direction in the figure and rotation thereof is stopped at a position where both the sensor 306a and the sensor 306b detect the shade (the black portions 307a and 307b). This position is referred to as a head position H0a (hereinafter referred to as H0a) and defined as the reference position of the head position. Explanation about movement of a printing-head position: Movement of the head position upon the printing will be explained. The gear 305 is rotated from H0a in the clockwise direction in the figure and stopped at a position where the sensor 306a detects the light. This position is referred to as H1a. Next, the gear 305 is rotated in the clockwise direction in the figure and stopped at a position where the sensor 306a detects the shade (the black portion 307b). This position is referred to as H2a. Next, the gear 305 is rotated in the clockwise direction in the figure and stopped at a position where the sensor 306a detects the light. This position is referred to as H3a. Next, the gear 305 is rotated in the clockwise direction in the figure and stopped at a position where the sensor 306a detects the shade (the black portion 307c). This position is referred to as H4. Next, the gear 305 is rotated from H4 in the counterclockwise direction in the figure and stopped at a position where the sensor 306a detects the light once and then detects the shade (the black portion 307b). This position is referred to as H3b. Next, the gear 305 is rotated in the counterclockwise direction in the figure and stopped at a position where the sensor 306a detects the light. This position is referred to as H2b. Next, the gear 305 is rotated in the counterclockwise direction in the figure and stopped at a position where the sensor 306a detects the shade (the black portion 307a). This position is referred to as H1b. Next, the gear 305 is rotated in the counterclockwise direction in the figure and stopped at a position where both the sensor 306a and the sensor 306b detect the shade. This position is referred to as H0b. Here, as shown in Figures 18A-18D, a positional relation of the gear 305 and the sensor 306a and the sensor 306b under a state of H2a and H2b positions, a positional relation of the cam groove 308a and a pin 320a of a follower 320 connected to the head arm 312, a positional relation of the cam groove 308b and a pin 142a of the change arm 142, and a positional relation of the cam groove 309b and a pin 328a of the cam lever 328 are shown in Figure 18A, Figure 18B, Figure 18C and Figure 18D, respectively. The motor 300 is stopped immediately after the H2a or H2b position is detected, so that difference in position of the gear 305 between the stop positions H2a and H2b is only a little. If the H2a and H2b positions are compared, the respective pins are located in a profile of the same radius of the cams, so that if a rotation center of each of the cams is defined as reference, then relative positions of the respective pins at H2a and H2b are the same. Therefore, since the follower 320, the cam lever 328 and the change arm 142 are located at the same position at the H2a and H2b positions, the H2a and H2b positions can be regarded as the same in view of the control of the printer. Hence, the H2a and H2b positions will be referred to as H2 in the following explanation. Similarly, since the respective pins are set to be stopped at the stop positions in the profile of the same radius of the cams upon the H0a and H0b, the H1a and H1b and the H3a and H3b positions, the H0a and H0b, the H1a and H1b and the H3a and H3b positions will be referred to as H0, H1 and H3 in the following explanation, respectively. H4 is detected only when the gear 305 is rotated in the clockwise direction in the figure. Also, Figure 17B shows a positional relation of the cam groove 308a and the pin 320a of the follower 320 connected to the head arm corresponding to the respective positions H0 to H4 of the gear 305. Figure 17C shows a positional relation of the cam groove 308b and the pin 142a of the change arm 142 corresponding to the respective positions H0 to H4 of the gear 305. And Figure 17D shows a positional relation of the cam groove 309b and the pin 328a of the cam lever 328 corresponding to the respective positions H0 to H4 of the gear 305. Movement of the head position upon the reading of the ribbon code: After the reference position H0 is detected, the gear 305 is rotated in the counterclockwise direction in the figure and stopped at a position where after shade detection of the black portion 307a at the H0 position, the sensor 306a detects the light once, detects the black portion 307b and further detects the black portion 307c. This position is referred to as H3'. The H3' position is the same as the H3 position in view of the stop position of the gear 305, but operations of the cam plane 308a and the cam plane 308b at H3' are different from those at H3, so that these positions are distinguished. After detection of the H3' position, the gear 308 is rotated in the clockwise direction in the figure and then returned to the reference position H0. Explanation about operations of the cams 308 and 309: Shapes of the respective cam grooves 308a, 308b and 309a will be explained with reference to Figures 19 to 21. As shown in Figure 19, the cam groove 308a is composed of passages 308a0, 308a1, 308a2 and 308a3 located in a concentric-circle fashion relative to the rotation center of the cam 308, curve passages connecting smoothly the passages 308a0 and 308a1, the passages 308a1 and 308a2 and the passages 308a2 and 308a3 and a curve connecting smoothly the passage 308a3 and the middle of the passage 308a0. A pin 318a of the link 315 is stopped in the passage 308a0 upon the positions H0, H1 and H3' and stopped in the passages 308a1, 308a2 and 308a3 upon the H2, H3 and H4 positions, respectively. As shown in Figure 20, the cam groove 308b is composed of passages 308b0, 308b1, 308b2 and 308b3 located in a concentric-circle fashion relative to the rotation center of the cam 308, curve passages connecting smoothly the passages 308b0 and 308b1, the passages 308b1 and 308b2 and the passages 308b2 and 308b3 and a curve connecting smoothly the passage 308b3 and the middle of the passage 308b0. The pin 142a of the change arm 142 is stopped in the passage 308b0 upon the positions H0 and H3', and is stopped in the passages 309b1 and 308b2 upon the H1 and H2 positions, respectively, and is stopped in the passage 308b3 upon the H3 and H4 positions. As shown in Figure 21, the cam groove 309b is composed of a passage 309b0, a passage 309b1 located in a concentric-circle fashion relative to the rotation center of the cam 309 and curves smoothly connecting both of ends of the passages 309b0 and 309b1. The pin 328a of the cam lever 328 is stopped in the passage 309b0 upon the position H0 and in the passage 309b1 upon the positions H1, H2, H3, H3' and H4, respectively. Operation of the respective head positions and the cams: Initial operation With the gear 305 being first rotated in order to detect the reference position 0, the cam 308 and the cam 309 are similarly rotated in the clockwise direction in the figure. Although a branch point 308a4 to the passage 308a3 and a branch point 308b4 to the passage 308b3 are provided in the passage 308a0 of the cam groove 308a and the passage 308b0 of the cam groove 308b, respectively, if the cams are rotated in the clockwise direction in the figure, then a pin 312a and the pin 142a are prevented from disturbing the rotations of the respective cams. Explanation about construction of the head arm 312: As shown in Figure 22, a pair of the head arms 312 are rotatably supported by a shaft 319, and a pair of the levers 320 and a pair of arms 321 are rotatably supported by the same shaft 319, to which a pair of fixed plates 311 (see Figure 3) fixed at a part thereof on the covering plate 404 is fitted. The shaft 319 is supported by the chassis 401. Also, a pair of followers 319a are fixed on the shaft 319. The pins 320a of a pair of the levers 320 are coupled to links 313. To the links 313, links 314 and links 315 are coupled through pins 316. The other pins 317 of the links 314 pierce through the long apertures 312a of the arms 312. The other pins 318 of the links 315 are engaged with the cam groove 308a of the cam 308 through an aperture 319b of the followers 319a fixed on the shaft 319. The head arms 312 are disposed between the links 314 and the arms 321 which are connected by the pins 316. The pins 317 are connected to the arms 321 through the long apertures 312a of the head arms 312. The head arms 312 and the arms 321 are biased by springs 327 so as to draw each other, while relative movement amounts thereof are restricted by the pins 317 and the long apertures 312a with employing the shaft 319 as the rotation center thereof. Also, the arm 321 is biased by a spring 326, and by this force the follower 319a is biased in the center direction of the cam 308. A heat sink 322 is fitted to a pair of the head arms 312. To the heat sink 322, a head 323 and a ribbon guide 324 serving also as a reflection mirror are fitted. The head 323 is provided with a large number of heating bodies and wiring members (not shown) for supplying electricity to the heating bodies and a head cover 325. Explanation about movement of the head 323: Movement of the head arm will be explained with reference to Figures 23A-23D. The head 323 is given four stop positions. As shown in Figure 23A, when the gear 305 is stopped at the H0 and H1 positions, the head 323 is located at a standby position. As shown in Figure 23B, when the gear 305 is moved to the H2 position, the head 323 is moved so that a plane portion 324a of the ribbon guide 324 should be moved in front of optical reflection type ribbon-mark sensors 427a and 427b fitted to the guide 426. Here, a detecting method of the header mark 11 and the patch mark 12 of the ribbon will be explained. The ribbon guide 324 is made of a material which is made by subjecting a stainless plate to a mirror-like finishing and has high optical reflectance. The header mark 11 and the patch mark 12 of the ink ribbon 10 are belt-shaped marks having low optical transmittance and reflectance. Since portions except the header mark 11 and the patch mark 12 of the ink ribbon 10 have high optical transmittance, when there is the ink ribbon 10 between the sensors and the plane portion 324a, the sensor 427a and the sensor 427b detect the ribbon- guide plane portion 324a as light. When there are the above marks between the sensors and the plane portion 324a, the sensors detect the plane portion as shade. Since the header mark 11 is set to be a belt-shaped one over the entire ribbon width, both of the sensors 427a and 427b detect the black portion. Since the patch mark 12 is set to be a belt-shaped one over about half of the ribbon width including a detection range of the sensor 427a, the sensor 427a and the sensor 427b detect the shade and the light, respectively. Next, as shown in Figure 23C, when the gear 305 is moved to the H3 position, the head 323 is moved to a position where there is a little space between the head and a platen 412. The head 323 is moved to the H3 position, whereby the printer according to the present invention changes a carrying passage of the paper. The detail thereof will be described later. As shown in Figure 23D, when the gear 305 is moved to the H4 position. the head 323 is pressed on the platen 412. The respective links are driven by the cam 308. The arm 321 rotates the head arm 312 in the direction to the platen 412. At last, the head 323 is brought in contact with the platen 412. Further, the arm 321 is rotated by the cam 308 thereafter, but since the head 323 is already in contact with the platen 412, the head arm 312 cannot be rotated. Therefore, the arm 321 and the head arm 312 are relatively rotated, and the restriction of the above pin 316 and a long aperture 321a of the head arm 312 is released. Then, the head arm 312 presses the head 323 on the platen 412 through the spring 327. Explanation about construction of the change arm 142: The change arm 142 is rotated by the cam groove 308b and given four stop positions shown in Figures 24A-24D. The change arm 142 is rotatably supported by a supporting shaft 142C and drives a locking click 143 and a brake click 144, which are rotatably supported by the bracket 100. The locking click 143 and the brake click 144 are respectively engaged with the gear portion 146 of the S reel base 146 and the gear 145 to prevent the respective gears from rotating. Also, the change arm 142 drives the link 149 connected thereto by a shaft 149c. The link 149 is guided at an aperture portion 149b thereof by the rotation shaft 146c of the S reel base 146, and movement of the link 149 permits the link head portion 149a to prevent or release the engaging of the pendulum gear 124 with the gear 145 of the S reel base 146. Figure 24A shows a state in which the gear 305 is located at the H0 and H3' positions. In this state the locking click 143 is engaged with the gear portion 146a, the brake click 144 is released, and the link 149 does not restrict movement of the pendulum gear 124. Figure 24B shows a state in which the gear 305 is located at the H1 position. In this state both of the locking click 143 and the brake click 144 are released, and the link 149 does not restrict movement of the pendulum gear 124. Figure 24C shows a state in which the gear 305 is located at the H2 position. In this state both of the locking click 143 and the brake click 144 are released, and the link 149 restricts movement of the pendulum gear 124. Figure 24D shows a state in which the gear 305 is located at the H3 and H4 positions. In this state the locking click 143 is released, the brake click 144 is engaged with the gear 145, and the link 149 restricts movement of the pendulum gear 124. Explanation about construction of the cam lever 328: The cam lever 328 is rotated by the cam groove 309a with a supporting shaft 328b as a center. The cam lever 328 is given two stop positions, as shown in Figures 25A and 25B, respectively. A head portion 326a of the cam lever 328 restricts movement of a pendulum arm 331 and can also slide the locking lever 332 slidably supported by the holder 422 (see Figure 9) with movement of a pin 328c of the cam lever 328. As to a pendulum gear 330 and the pendulum arm 331, when the cam 308 is rotated by a friction force generated by a spring (not shown) or the like in the clockwise direction in the figure,, rotation is transmitted from the gear portion 309b of the cam 309 to the two-stage gear 329 rotatably fitted to a shaft end of the shaft 319. Then, the pendulum arm 331 is rotated, and the pendulum gear 330 is engaged with the gear 22 of the code ring 21 to rotate the code ring 21. Figure 25A shows a state in which the gear 305 is located at the H0 position. In this state the cam lever 328 restricts the pendulum arm 331 to prevent the pendulum gear 330 from being engaged with the gear 22, and the locking lever 332 is moved backward to allow the ribbon door 420 to be opened. Figure 25B shows a state in which the gear 305 is located at the H1, H2, H3, H3' and H4 positions. In this state the cam lever 328 does not restrict the pendulum arm 331 from moving the pendulum gear 330 into engagement with the gear 22, and the locking click 421 is locked by the locking lever 332 to make it impossible to open the ribbon door 420. Lastly, a rotating method of the ribbon code ring 21 will be explained. After the gear 305 is positioned at the H0 position, the gear 305 is rotated in the clockwise direction in the figure and moved to the H3' position. Next, the gear 305 is rotated in the counterclockwise direction in the figure and returned to the H0 position again. At this time, during the movement thereof from the H3' position to the H0 position, the pendulum gear 330 is engaged with the gear 22 to rotate the ribbon-code ring 21, and the information mark 23 is read by a sensor 335. During this operation, the pin 318 of the head arm 312 is moved within the passage 308a0 of the cam groove 308a, so that the head arm 312 is not moved. Similarly, the pin 142a of the change arm 142 is moved within the passage 308b of the cam groove 308b, so that the change arm 142 is not moved. Therefore, in view of the printer, only the portion driven by the cam 309a is moved, while the other portions remain stationary. Also, during the reading of the information mark, the ribbon door 420 cannot be opened, Whereby the misreading of the information mark caused by the touch of a user is prevented. Next, a series of operations of printing operations will be explained with reference to Figures 26 to 31. Initialisation The following initialisations are performed after a power-source switch is turned on. Initialisation of the paper position: It is confirmed that the paper position is located at the P0, as shown in Figure 26. If the paper position is not located at P0, then the motor 101 is rotated to move the paper position to P0. Initialisation of the head position: It is confirmed that the head position is located at H0, as shown in Figure 26. If the head position is not located at H0, as then the motor 300 is rotated to move the head position to H0. If the P0 and the H0 positions cannot be confirmed, then the printer is judged as having trouble. Confirmation of the ink ribbon 10 and the reading of the ribbon code: It is confirmed with a switch (not shown) that the ribbon door 420 is closed, and it is confirmed with a switch 428 that the ribbon cassette 1 is loaded. If they are confirmed, then the motor 300 is rotated to thereby rotate the ribbon code ring 21 whereupon the information mark 23 is read by the sensor 335. If the information mark 23 is not matched with various information marks previously stored in the set, then it is judged that the ribbon cassette I is not loaded, and then an alarm is given. Also, if the switch (not shown) of the ribbon door 420 and the switch 428 of the ribbon cassette I are turned ON/OFF while the set is kept on standby, then it is judged that the ribbon cassette 1 is exchanged, and the ribbon code is read again. Printing operation Printing operation is started by pushing a switch or the like. Confirmation of the paper feeding tray 200 and the printing paper: It is confirmed by a switch 429 (see Fig- 3) that the paper feeding tray 200 is loaded, and it is confirmed by sensors 430a and 430b that there is the printing paper 202 in the paper feeding tray 200. If they cannot be confirmed, then it is judged that there is no printing paper therein, and an alarm is given. Head searching of the ink ribbon 10 and movement of the head position: The head position is moved from the H0 position shown in Figure 26 to the H2 position shown in Figure 27, and until the sensor 427a and the sensor 427b detect the header mark 11 of the ink ribbon 10, the motor 101 is rotated, and the ink ribbon 10 is wound by rotation of the T reel base 111 to search for the header mark 11 of the ink ribbon. Since a rotation time of the motor 101 is set in advance, if the header mark 11 can not be detected even when the motor 101 is rotated for the set time, then it is judged that there is not enough remaining ribbon, and an alarm is generated. Movement of the paper position: The motor 101 is rotated to move the paper position from P0 to P1. That is, the rotation of the motor 101 permits the paper feeding arm 204 to be moved upward by the paper feeding cam 416 through the gear 118, and then the printing paper 202 is brought upward and then pressed on the paper feeding roller 213. Then, the printing paper 202 is drawn inside by the paper feeding roller 213 and sandwiched between the paper feeding roller 212 and the separating roller 214 to feed the paper. The carrying of the printing paper and detection thereof by a paper feeding sensor 224: The stepping motor 102 is rotated to carry the printing paper 202 until the paper feeding sensor 224 detects the paper. If the printing paper is not detected by the paper feeding sensor 224 after the stepping motor 102 is rotated by a certain amount, then it is judged as a paper feeding error, and an alarm is given. Movement of the paper position: A position where a head of the printing paper 202 is detected by the paper feeding sensor 224 is defined as a reference, and the printing paper is carried by a predetermined amount therefrom. The printing paper is held between the capstan 410 and the pinch roller 411, and thus, is caused to advance when the motor 102 is rotated. The paper is moved from the paper position P1, as shown in Figure 28, to the position P2, as shown in Figure 29, when the motor 101 is rotated. The pushing down of the printing paper and movement of the head position: Subsequently, when a position where the head of the printing paper is detected by the paper feeding sensor 224 is defined as a reference and the printing paper is carried by a predetermined amount therefrom, the head of the printing paper is located below the head cover 325. While the head of the printing paper lies below the head cover 325, the motor 300 is rotated to move the head position from the position shown in Figure 23B to that shown in Figure 23C, whereby the head position is moved from the H2 position shown in Figure 28 to the H3 position shown in Figure 29. The head of the printing paper moving substantially in the center direction of the S reel base 146 is pushed by the head cover 325 to thereby change its moving direction to a direction of a passage M formed of the chassis 401 and a guide 406. When the printing paper is carried further, the head of the printing paper 202 is led into the passage M. Detection thereof by a sensor 415: When the printing paper 202 is further carried, the head of the printing paper is detected by the sensor 415. If the printing paper is not detected by the sensor 415 even when carried from a position of the paper feeding sensor 224 by a predetermined amount, then it is judged that a paper feeding error is caused, and then an alarm is given. Detection of a rear end of the printing paper by the paper feeding sensor 224: When the printing paper 202 is further carried, the rear end of the printing paper is detected by the paper feeding sensor 224. Length (in the carrying direction) of the printing paper is detected on the basis of a number of steps taken by the stepping motor 102 from the detection of the head of the printing paper by the paper feeding sensor 224 to the detection of the rear end of the printing paper thereby. The detected length of the printing paper 202 is compared to a length of predetermined kinds of printing papers, whereby the kind and size of the printing paper is judged. If the paper is a paper having a size other than one of the predetermined sizes, or the discriminated kind of the printing paper does not correlate with the kind of the ink ribbon previously discriminated from the information mark 23 of the ribbon cassette 1, then an alarm is given. 3-mm skip of the printing paper: After the above detection of the rear end of the printing paper by the paper feeding sensor 224, the printing paper is successively carried a distance of 3 mm in the paper feeding direction to perform the detection thereof by the paper feeding sensor 224. If the printing paper is detected again by the paper feeding sensor 224 while the paper is carried the 3 mm distance, then it is judged that the former detection is based on a print of a rear surface of the printing paper, stains or the like, and then the second detected position is set to the true rear end of the printing paper. Movement of the printing paper to the printing position: The printing paper is carried by a predetermined amount (several mm) from the position where the rear end of the printing paper is detected, whereby the printing paper is moved to the printing position and then stopped. Movement of the head position: The motor 300 is rotated to change the operation from the one shown in Figure 23C to the one shown in Figure 23D, whereby the head 323 is pressed on the platen 412, and the head position is moved from the H3 position shown in Figure 29 to the H4 position shown in Figure 30. Printing processing The motor 101 is rotated to take up the ink ribbon 10 by the rotation of the T reel base 111, and at the same time, the stepping motor 102 is reversely rotated to carry the printing paper 202 in the opposite direction to the above carrying direction by reversal rotation of the capstan 410. Then, the printing is performed by the head 323. Movement of the head position and removal of slack of the ink ribbon: The motor 300 is rotated to move the head position from the H4 position shown in Figure 30 to the H2 position shown in Figure 31, and the motor 102 is reversely rotated for a predetermined time to thereby engage the pendulum gear 124 with the S reel base 146. Then, the S reel base 146 is rotated in the take-up direction to remove the slack of the ink ribbon 10. The head searching of the ink ribbon 10 and movement of the head position: The motor 101 is rotated until the sensor 427a and the sensor 427b detect the patch mark 12 of the ink ribbon 10 in the next printing operation. The T reel base 111 is rotated in the, take-up direction of the ribbon to take-up the ink ribbon 10 and search the head of the ribbon. Since the rotation time of the motor 101 is previously determined, if the patch mark 12 cannot be detected after the motor 101 is rotated for the set time, it is judged that there is not enough remaining ink ribbon, the ribbon is cut or the like. Then, an alarm is given. The pushing down of the printing paper and movement of the head position: In the same way as the pushing down of the paper upon the paper feeding, the position where the head of the printing paper is detected by the paper feeding sensor 224 is defined as a reference. The printing paper is carried by a predetermined amount therefrom. The head of the printing paper is located below the head cover 325. While the head of the printing paper 202 is located below the head cover 325, the head position is moved from the H2 position shown in Figure 28 to the H3 position shown in Figure 29 by changing the head position from the one shown in Figure 23B to the one shown in Figure 23C. Then, the head 323 pushes the printing paper 202 down. In the above printing operation on the printing paper 202, the above printing processing is repeated a total of four times in case of colour printing in order to subject the paper to the printing with respective colours and lastly subject a surface thereof to coating processing. Movement of the head position and removal of the slack of the ink ribbon: The motor 300 is rotated, and the head position is moved from the one shown in Figure 23D to the one shown in Figure 23B to thereby move the same from the H4 position shown in Figure 30 to the H2 position shown in Figure 31. Also, the motor 102 is reversely rotated for a predetermined time to thereby engage the pendulum gear 124 with the S reel base 146. Then, the S reel base 146 is rotated in the take-up direction to remove the slack of the ink ribbon 10. Delivery of the printed paper The capstan 410 is rotated by reverse rotation of the stepping motor 102, and the paper delivering roller 225 is rotated by reverse rotation of the motor 102, to thereby deliver the printing paper 202 through the paper delivering opening 703. If a paper delivering sensor 227 detects the printing paper after a predetermined amount of the paper is carried, then it is judged as a paper delivery error. Then, an alarm is given. As explained above, the printer according to the present invention is formed of the motor 101 which rotates the T reel base 111 and takes up the ink ribbon 10 to search the optional head of the ink ribbon, the stepping motor 102 for feeding and delivering the printing paper and removing the slack of the ink ribbon by the rotation of the S reel base 146, and the motor 300 for performing the discriminating operation of the ribbon code ring 21 and the printing operation by the head 323. The three motors 101, 102 and 300 allow the printer to operate without interlocking the movement of the head 323 with the capstan 410, the paper feeding arm 204 and the separating roller 214. The passage of the printing paper 202 is checked by the three sensors, that is, the paper feeding sensor 224, the sensor 415, and the paper delivering sensor 227. Therefore, even in the case of a jam of the printing paper 202, interruption during the printing operation or the like, the printing paper can be carried, and the ink ribbon can be taken up while the head is being moved at the most proper timing, so that when the power source is supplied again, operation can be automatically restored. Also, a conventional link mechanism for driving the capstan and the paper feeding mechanism is abolished, whereby miniaturisation of the printer can be realised. The head 323 can be freely moved, whereby the printing paper can be pushed down and the passage of the paper can also be provided at the printing unit. Therefore, the printer can be further miniaturised. Also, the cam 308 for operating the head 323 is provided as described above, whereby even when the code ring 21 of the ribbon code is rotated, the head 323 and other members are prevented from being moved unnecessarily. Also, the slack portion of the ink ribbon 10 can be rewound around the S reel base 146 in co-operation with the cam 308 of the head 323 and the stepping motor 102. Therefore, when the printing paper 202 and the ink ribbon 10 are not matched with each other, the printing paper is automatically delivered, and the ink ribbon 10 is rewound, whereby wasteful use of the ink ribbon can be prevented. The present invention is not limited to the above-mentioned embodiment shown in the drawings, but rather, is also intended to cover all modifications which can be effected without deviating from the scope of the invention.

Claims: A video signal printing apparatus comprising: a cassette (1) comprising a supply reel (13), a take-up reel (14), and a ribbon (10) wrapped around said reels; a main chassis (401) for receiving said cassette; a capstan (410) and a pinch roller (411) for feeding a paper (202) to a paper printing position; a motor means (102) for rotating said capstan (410) and said pinch roller (411); a platen for receiving the paper in said paper printing position, said platen being disposed in a position downstream of said capstan (410) and pinch roller (411) in a feeding direction; a head means (323) for heating and pressing said ribbon (10) onto the paper (202) in said printing position, said head means (323) being movable between a head printing position in which said ribbon is pressed onto said paper and a head waiting position in which said head releases said ribbon from said paper; a control means (308, 142) for selectively moving said head means (323) between said head printing position and said head waiting position, and for causing a slack of the ribbon to wind up onto said supply reel (13) upon said head means moving to said head waiting position, characterised in that the apparatus further comprises a pendulum gear means (124) drivingly connected to said motor means (102) for selectively driving said supply reel (13) for winding said slack of ribbon. The video signal printing apparatus according to claim 1, wherein said pendulum gear means (124) drives said supply reel (13) upon rotation of said motor means (102) in a first direction, and disengages from said supply reel upon rotation of said motor means (102) in a second direction. The video signal printing apparatus according to claim 2, wherein said control means (308, 142) prevents said pendulum gear (124) means from moving into driving engagement with said supply reel (13) when said head means (323) is in said head printing position. The video signal printing apparatus according to claim 3, wherein a torque limiting means (146) is provided between said pendulum gear means (124) and said supply reel (13) for limiting driving torque of said supply reel when winding said slack of ribbon.

Inventors: BUNYA TAKASHI, IIMA SHIN, KAMODA HITOSHI, MAEKAWA TOMOHIRO, YUI YASUJI, BUNYA, TAKASHI, IIMA, SHIN, KAMODA, HITOSHI, MAEKAWA, TOMOHIRO, YUI, YASUJI
Applicants: SONY CORP, SONY CORPORATION
Application year: 1994
Main classification: B41J17
IPC codes: B41J17, B41J32, B41J2